The present invention relates to subterranean operations, and more particularly, to environmentally compatible defoaming agents and methods of using such defoaming agents in subterranean well fluids.
When drilling or completing wells in subterranean formations, various fluids may be used for a variety of reasons. These fluids are often aqueous. For the purposes herein, such a fluid will be referred to as a “well fluid.” Common uses for well fluids include, but are not limited to: lubrication and cooling of drill bit cutting surfaces while drilling generally or drilling-in (e.g., drilling in a targeted petroliferous formation); transportation of cuttings to the surface; controlling formation pressure to prevent blowouts; maintaining well stability; suspending solids in the well; fracturing the formation; cementing the well; displacing the fluid within the well with another fluid; cleaning the well; testing the well; and minimizing fluid loss into and stabilizing the formation through which the well is being drilled. Similar fluids also may be used in other applications such as tunnel drilling. Fluids used for such purposes are encompassed within the term “well fluid” as used herein.
Where surfactants are included in a well fluid that does not include a classical surfactant foam, foaming is likely to occur. This foaming may be undesirable. On the other hand, surfactants may be added to generate desirable foam to assist in removing the particulate products of drilling, or for other purposes. The term “foam” and its derivatives as used herein refers to both instances of entrained gas and gas bubbles that exist on the surface of a fluid. Oftentimes, defoaming agents commonly are utilized, for example, as components in well treatment fluids, to prevent the formation of foam or to break a formed foam (i.e., reduce the amount of foam present in the fluid) (both are referred to collectively herein as “breaking” the foam) during the preparation and placement of the well treatment fluid in the subterranean formation. “Defoaming agents” are well fluid additives that may lower interfacial tension in a well fluid so that gas trapped in a foam will readily escape from the well fluid. Defoaming agents also may be used to treat a foam in a return fluid to facilitate disposal of the fluid. Additionally, defoaming agents often are included in cement compositions, inter alia, to ensure proper mixing and to provide adequate control over the density of the cement composition.
A variety of defoaming agents are well known in the art. Dodecyl alcohol, aluminum stearate, various glycols, silicones and sulfonated hydrocarbons are examples of conventional defoamers. Many conventional defoamers have undesirable environmental characteristics and/or may be limited by strict environmental regulations in certain areas of the world. Moreover, many defoaming agents that comply with these strict environmental regulations may be relatively expensive and/or may suffer from other drawbacks, such as poorer defoaming performance.